This invention relates in general to barrier coatings, and in particular to a welding machine maintenance coating that prevents the adhesion of weld spatter on the welding machine and other areas where weld spatter is a problem. This coating often prevents the buildup of weld slag, and when buildups of weld slag occur, it makes for easy clean up of weld slag off welding machines and areas where weld spatter causes a buildup of weld slag.
Automated and robotic controlled welding is often used in the assembly of a product. In the process of welding, molten metal often flies away from the welding location. This molten metal is commonly referred to as weld spatter. When this molten metal cools, it is commonly referred to as weld slag. In automated or robotic controlled spot welding, weld spatter is often produced which can fly as far as fifty feet from the welding location. This weld spatter often flies in the same direction producing buildups of weld slag on automated machinery. Often automated or robotic controlled welders are manufactured to tight dimensional tolerances and these buildups of weld slag often accumulate enough to produce out of specification parts and/or prevent the welding machine from operating. This produces costly quality issues, production downtime and requires maintenance to remove the weld slag off the welding machine. Weld slag is commonly removed by wire brushing, scraping, prying, chiseling, and grinding. This is often a very labor intensive, tedious, and time consuming process which often creates further breakdowns on the automated welding machinery.
Currently available weld anti-spatter products are formulations using organic materials for release agents. A very common weld spatter release coating is based on soy lecithin and soybean oil or other vegetable oils. This product is often supplied in aerosol cans pressurized with methylene chloride or CO2. The product is typically sprayed on the metal to be welded or on the welding nozzle to prevent the adhesion of weld spatter to the nozzle. Other common weld anti-spatter materials are gel products that are often petrolatum or thickened lecithin or vegetable oils. Another weld anti-spatter product is described in U.S. Pat. No. 4,861,392 to Grabe where a typical composition is composed as follows. 5-6% micronized graphite, 51-60% limestone, 34-38% water, 0.5-1% morpholine, 0.2-0.4% polysorbate 80, 0.2-1.0% potassium alginate, 0.02-1.2% Natrosol LR70, and 0.01-1.0% Kelzan. These products are somewhat effective but have two major drawbacks. First, they are only effective for a limited period mainly because they decompose. Second, in the process of decomposition, the products produce noxious odors, fumes, and smoke. Since weld spatter is composed of molten iron metal, being at approximately 1300xc2x0 C. the weld spatter readily decomposes organic materials producing noxious decomposition products. Since there is usually only general ventilation in these areas, these noxious fumes can make production workers ill. For these health and safety reasons and their limited time of effectiveness, the current weld-spatter products have not gained acceptance for use as a maintenance coating for automated welding machinery. Currently there is a need in the automated welding industry for an effective weld maintenance coating that will reduce or eliminate down time related to weld slag for extended periods of time and be free of producing noxious odors.
This invention relates to a method of preventing a material from adhering to a surface. In a preferred embodiment, the material comprises weld spatter and the surface is located near a welding operation. The method comprises coating the surface with a slurry comprising a mineral material in water. The slurry contains from about 10% to about 70% solids by weight and not more than about 5% by weight of a material that decomposes when heated to 1000xc2x0 F. for one minute. The slurry is allowed to dry to form a barrier coating before the material contacts the surface.
In another embodiment of the invention, the barrier coating binds to the surface such that from about 50 to about 200 finger double rubs are required to reach the surface when the dry barrier coating is 30 microns thick.
In another embodiment of the invention, the barrier coating dries in a time not longer than about 20 minutes when the slurry is applied as a 250 micron thick wet film and with the temperature at 72xc2x0 F. and air moving over the film at 110 feet per minute.
Various advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.